Interference control in a broadband powerline communication system

ABSTRACT

A broadband powerline communication system makes use of knowledge of the spectrum characteristics of a local radio environment in order to improve system performance. A determination is made of the spectrum characteristics of a radio environment in the vicinity of the broadband powerline communication system that is transmitting data on modulated carrier frequencies. In order to avoid interference, certain ones of the carrier frequencies otherwise used by the broadband powerline communication system may be selectively masked based on the determination. The spectrum characteristics may be determined 1) in advance and used to compile a configuration database comprising frequency masking parameters; 2) by monitoring the local radio environment using the transmitter/receiver nodes of the system; or 3) based upon receipt of an indication from a conflicting user that the user is experiencing interference. Various combinations of these spectrum characteristic determination techniques may also be used.

This application claims the benefit of U.S. Provisional Application No.60/632,326 filed Dec. 1, 2004, which is incorporated herein byreference.

BACKGROUND OF THE INVENTION

The present invention relates generally to broadband powerlinecommunication systems, and more particularly to interference control ina broadband powerline communication system.

The use of power lines to transmit data is known. Initially, powerlinecommunication systems were limited to relatively low data rates,typically less than 500 kbs. These low data rates are generally usefulfor applications such as remote control of various switches connected tothe powerline system. More recently, developments have been made in thearea of broadband powerline communication systems, also known aspowerline telecommunications (PLT) systems or broadband powerline (BPL)systems. These systems are capable of transmitting data at significantlyhigher data rates than previous systems. For example, BPL systems cantransmit data at rates of 4-20 Mbps.

While existing powerline systems are capable of transmitting data at therates described above, they were not initially designed for datatransmission. Instead, they were designed to carry large currents athigh voltages so that significant amounts of energy could be distributedat one primary low frequency (e.g., 60 Hertz).

Powerline communication systems generally use one or more carrierfrequencies in order to spread the data transmission over a wider rangeof frequencies. The low data rate powerline communication systemsdiscussed above generally utilized frequencies in the range of 9 kHz to525 kHz. In this frequency range the risk of emissions is low primarilybecause the wavelengths used in the signaling are long with respect tothe typical cable lengths in the system. However, the high data rates ofBPL systems cannot be achieved using carrier frequencies below 525 kHz.Instead, BPL systems typically use carrier frequencies in the range of1-30 MHz. At these higher frequencies the powerline cables become moreeffective radiators of electromagnetic waves.

One of the problems with a BPL system is the risk of interference, bothoutbound and inbound. Outbound interference refers to interference toradio communications services caused by the generation ofelectromagnetic emissions from the powerlines over which the BPL systemoperates. Inbound interference refers to the detrimental effects ofinbound interference from external electromagnetic radiators. Thephysical attributes of the powerlines (e.g., high elevation andunshielded wiring) along with the higher carrier signal frequenciesneeded for high bandwidth data transmission, contribute to thisinterference problem.

BRIEF SUMMARY OF THE INVENTION

The present invention provides improved techniques for reducinginterference in a broadband powerline communication system wherebyknowledge of the spectrum characteristics of a local radio environmentare used in order to improve the performance of a BPL system. Inaccordance with the principles of the invention, a determination is madeof the spectrum characteristics of a radio environment in the vicinityof a broadband powerline communication system that is transmitting dataon modulated carrier frequencies. Since the frequencies used by thebroadband powerline communication system are shared with other users,and not used exclusively by the broadband powerline communicationsystem, knowledge of spectrum usage by potentially conflicting users maybe used to reduce interference. More particularly, certain ones of thecarrier frequencies otherwise used by the broadband powerlinecommunication system may be masked (i.e., not used) by all or part ofthe broadband powerline system in order to avoid interference.

In a first embodiment of the invention, the spectrum characteristics inthe vicinity of the broadband powerline system are determined in advanceand used to compile a database of known conflicting users and thecharacteristics of their spectrum usage. The compilation and analysis ofthis information will allow for the maintenance of a configurationdatabase comprising frequency masking parameters which may be used inorder to dynamically configure the broadband powerline communicationsystem. The frequency masking parameters may include, for example, theparticular frequency or frequencies used, the days and/or times thefrequencies are used, and the geographic area in which the conflictinguse may result in interference. Using this information, the system maymask out particular frequencies, in particular geographic locations, atparticular times, in order to reduce interference. In one embodiment ofthe invention, an interference controller node controls the frequencymasking by transmitting control instructions to particulartransmitter/receiver nodes based on the frequency masking parameters inthe database.

In a second embodiment of the invention the radio environment in thevicinity of the broadband powerline communication system is monitored inorder to detect conflicting users. Certain ones of the carrierfrequencies are then masked based on the monitoring. In a particularembodiment, the monitoring is performed by the transmitter/receivernodes by monitoring the various received frequencies to determine ifthere is interference present on any of the frequency channels. Thismonitoring may be performed during a so-called quiet period, duringwhich the transmitter/receiver nodes are not transmitting data, but onlylistening for received signals on the broadband powerline communicationsystem. In one embodiment, the monitoring process may be initiated by aninterference controller node sending a control instruction to thetransmitter/receiver nodes. The transmitter/receiver nodes may send theinterference information to the interference controller node whereby theinterference controller node determines appropriate frequency masks andsends frequency masking control instructions to the transmitter/receivernodes.

In a third embodiment, frequency masks may be initiated based uponreceipt of an indication from a conflicting user that the user isexperiencing interference. In accordance with this embodiment, thebroadband powerline communication system transmits a unique identifieron at least one of the carrier frequencies used by the system. Receiptof this identifier by a user indicates that the user is receivinginterference from the broadband powerline communication system. When thebroadband powerline communication system receives a notification that auser has received the identifier, then the system may mask appropriatecarrier frequencies based on the receipt of the identifier from theconflicting user. In a particular embodiment, the unique identifier maybe some code, for example, that uniquely identifies the BPL system orthe service provider operating the BPL system. The identifier mayinclude other information as well. The identifier may be pre-programmedinto each of the transmitter/receiver nodes of the system.Alternatively, the identifier, along with an instruction to transmit theidentifier, may be sent in a control instruction from the interferencecontroller.

These and other advantages of the invention will be apparent to those ofordinary skill in the art by reference to the following detaileddescription and the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art broadband powerline communication system;

FIG. 2 illustrates interference in a broadband powerline communicationsystem and shows powerlines and user premises;

FIG. 3 shows a schematic block diagram of a broadband powerlinecommunication system;

FIG. 4 shows a block diagram of an interference controller; and

FIG. 5 shows an exemplary data structure for a database comprisingfrequency masking parameters.

DETAILED DESCRIPTION

A typical prior art powerline communication system 100 is shown inFIG. 1. A head end network node 106 is connected to a data network 102via a fiber optic cable 104. In accordance with a typical networkservice, the head end 106 is configured to transmit data to end userpremises (e.g., premises 108) using powerline cables as the transmissionmedium. The head end 106 is also configured to convert signals in theoptical domain received from fiber 104 to the electrical domain usingwell known optical to electrical conversion techniques. The head end 106is connected to a transmitter 110. The transmitter 110 contains amodulator 112 which modulates the data received from head end 106 onto acarrier signal using well known RF modulation techniques. As describedabove, typical carrier frequencies for a powerline communication systemare in the range of 2-30 MHz. The modulated signal is provided to thepowerline cable 114 via line 116 and coupler 118. A powerlinecommunication system 100 of the type shown in FIG. 1 may use orthogonalfrequency division multiplexing (OFDM) in which the available bandwidthis split up into multiple narrowband channels which do not interferewith each other. Thus, in accordance with OFDM transmission, multiplecarrier signals, each having its own frequency band and representing adistinct data channel, are carried over the cable 114.

For purposes of the present description, it is assumed that thepowerline cable 114 is a medium voltage (MV) powerline cable typicallysupplying power at 4-66 kV. Such medium voltage cable is typically analuminum cable having a 1 cm diameter. Coupler 118 couples the modulatedcarrier signal supplied by line 116 to the MV line 114. Various types ofcouplers 118 are known in the art. For example, coupler 118 may be aninductive coupler, a capacitive coupler, or may employ direct metalliccontact. One type of coupler which may be used is a coupler as describedin co-pending U.S. patent application Ser. No. 10/963,144, filed Oct.12, 2004, entitled Broadband Coupler Technique for Electrical Connectionto Power Lines. The carrier signal is transmitted along the length of MVpowerline cable 114 to coupler 120 which couples the signal from the MVpowerline cable 114 to a receiver 124 via line 122.

The signal from receiver 124 is provided to the premises 108 via lowvoltage (LV) powerline 128. The low voltage powerline typically suppliespower at 100-240 volts. Thus, one of the functions of the receiver is totranslate the data from the MV line to the LV line. The low voltage line128 is connected to a modem 130 within the premises 108. The modem 130demodulates the signal received from the MV powerline cable 114 andextracts the data that was transmitted from the head end 106. It isnoted that in particular embodiments, it is possible that the receiver124 further functions to demodulate the data and deliver it to a secondtransmitter (not shown) that would remodulate the data and send it tothe premises 108.

It is noted that for ease of description only downstream (i.e., fromhead end to end user) data transmission is shown and described. Oneskilled in the art would readily recognize that upstream transmissioncould be accomplished in a similar manner. Thus, in a bidirectionalsystem, transmitter 110 and receiver 124 may each be implemented as atransmitter/receiver.

As described above in the background section, one of the problems withBPL systems as shown in FIG. 1 is the effect of both inbound andoutbound interference. FIG. 2 illustrates this problem by showing thepowerlines 202 which are part of a BPL system and user premises 204,both of which are making use of the same RF frequency spectrum. Sincethe frequency spectrum used by a typical BPL system is not used solelyby the BPL system, there is the potential for interference asillustrated in FIG. 2. The user premises 204 represents a user that isoperating in the vicinity of the BPL system and is using at least aportion of the same frequency spectrum as the BPL system. As usedherein, the term conflicting user is used to identify any user or userdevice that is using at least some frequencies that are also used by theBPL system. If the conflicting user 204 is operating in the vicinity ofthe BPL system, then there is the potential for two types ofinterference. Transmissions from conflicting user 204 may be received bythe powerlines 202 and thus interfere with communications on the BPLsystem (referred to as inbound interference) and transmissions on theBPL system may be radiated from the powerlines 202 and received by theconflicting user 204 causing interference to the conflicting user(referred to as outbound interference). As seen from this discussion,the term conflicting user is used to identify a user that either causes(or has the potential to cause) interference to the BPL system, orreceives (or has the potential to receive) interference from the BPLsystem. Further, the use of the term inbound or outbound interference isused with respect to the BPL system and as such, outbound interferencefrom the BPL system would be inbound interference to the conflictinguser, and inbound interference to the BPL system would be outboundinterference from the conflicting user. As would be readily understoodby one skilled in the art, the term inbound or outbound is only relevantif the point of reference is known. Unless otherwise indicated herein,the point of reference used herein is that of the BPL system. As usedherein, the phrase—in the vicinity of a BPL system—means within ageographic area where there is potential inbound or outboundinterference with respect to the BPL system.

A schematic block diagram of a BPL system is shown in FIG. 3 in order tofurther describe the spectrum characteristics of a radio environment inthe vicinity of a BPL system. The BPL system of FIG. 3 shows a number ofBPL transmitter/receiver nodes 302, 304, 306, 308, 310 connected bypowerlines 320, 322, 324, 326 as shown. Each of the transmitter/receivernodes is capable of both transmission and receipt of modulated data onvarious frequencies as described above in conjunction with FIG. 1. Thus,each of the transmitter/receiver nodes 302, 304, 306, 308, 310 combinesthe transmitter and receiver functionality into a single node. Thus, inexemplary operation, node 302 will transmit data via powerline 320 tonode 304, node 304 will receive the transmitted data and will thentransmit the data to node 306 via powerline 322. This functionalitycontinues and the data will propagate along the BPL system. The datatransmission between any two transmitter/receiver nodes may usefrequencies which are the same as, or different from, the datatransmission between any two other nodes. This becomes especially usefulin the presence of a conflicting user. For example, consider conflictinguser 330 in the vicinity of the BPL system as shown in FIG. 3. Ifconflicting user 330 is transmitting on frequency channel x, thenpowerline 322 will receive this transmitted signal which will result ininterference in the communication channel between transmitter/receivernode 304 and transmitter/receiver node 306 if these nodes are usingfrequency channel x for data transmission via powerline 322. However,frequency channel x may continue to be used for data transmissionbetween other transmitter/receiver nodes (e.g., betweentransmitter/receiver node 306 and transmitter/receiver node 308 viapowerline 324) because the interfering signal from conflicting user 330is not strong enough to cause substantial interference on powerline 324.As illustrated in FIG. 3, the area of interference 332 usuallyencompasses only a limited area. It is to be noted that the area ofinterference with respect to any particular conflicting user may bedifferent for inbound interference and outbound interference due to thefact that the power of interfering signals radiated from the BPL systemmay be different than the power of interfering signals radiated from theconflicting user.

The converse situation is similar, in which the BPL system istransmitting data on frequency channel x between transmitter/receivernodes 304 and 306 via powerline 322, and is therefore radiating signalsinto the vicinity of the BPL system on channel x. As such, conflictinguser 330 will receive this transmitted signal which will result ininterference at the conflicting user 330. However, frequency channel xmay continue to be used for data transmission between othertransmitter/receiver nodes (e.g., between transmitter/receiver node 306and transmitter/receiver node 308 via powerline 324) without interferingwith conflicting user 330 because the interfering signal radiating frompowerlines other than powerline 322 will not be strong enough to causesubstantial interference at conflicting user 330. Again, as illustratedin FIG. 3, the area of interference 332 usually encompasses only alimited area.

In view of the above, knowledge of the spectrum characteristics of alocal radio environment can be used in order to improve the performanceof a BPL system in accordance with the principles of the presentinvention. In accordance with the principles of the invention, adetermination is made as to the spectrum characteristics of a radioenvironment in the vicinity of a BPL system that is transmitting data onmodulated carrier frequencies. Since the frequencies used by the BPLsystem are shared with other users, and not used exclusively by the BPLsystem, knowledge of spectrum usage by interfering users may be used toreduce interference. More particularly, certain ones of the carrierfrequencies otherwise used by the BPL system may be masked (i.e., notused) by all or part of the BPL system in order to avoid interference.Further details of the present invention will now be described inaccordance with several illustrative embodiments.

In a first embodiment of the invention, the spectrum characteristics inthe vicinity of the BPL system may be determined in advance and used tocompile a database of known conflicting users and the characteristics oftheir spectrum usage. Various information may be compiled in accordancewith this embodiment of the invention. For example, and withoutlimitation, such information about a conflicting user may include: theparticular frequency or frequencies used, the days and/or times thefrequencies are used, the geographic area in which the conflictinguser's transmitted signals may be strong enough to interfere with theBPL system, and the geographic area in which the BPL system'stransmitted signals may be strong enough to interfere with theconflicting user. The compilation and analysis of this information willallow for the maintenance of a configuration database which may be usedin order to dynamically configure the BPL system. If conflicting uses ofthe radio spectrum in a particular geographic area are known in advance,then those conflicting uses can be avoided by masking certain radiofrequencies in portions of the BPL system. For example, returning to theexample of FIG. 3, if it is known that conflicting user 330 istransmitting or receiving on frequency channel x, and area ofinterference 332 with respect to this conflicting user is also known,then the BPL system may mask out frequency channel x within the area ofinterference 332.

Additional information about the conflicting use may also be used inorder to configure the BPL system. For example, it may be known that theconflicting use of a particular frequency channel by a particularconflicting user only occurs on certain days, certain times, or somecombination of days and times. This information may be used in order tomask out certain frequencies only when necessary to avoid theinterference, so that the full spectrum may continue to be used at othertimes.

This information may be compiled in various ways. For example, a surveyof the geographic area in the vicinity of the BPL system may be made bytechnicians using various radio monitoring equipment so that over someperiod of time the spectrum usage characteristics may be determined.Alternatively, potential conflicting users in the geographic area maysupply information as to their usage of the radio spectrum. Anotheralternative is that the BPL system may detect various types ofconflicting use over time and collect this information for later use.Yet another alternative is that some central authority may notify theservice provider operating the BPL system about local spectrum usage.

An apparatus which may be used in order to implement an embodiment ofthe invention is shown in FIG. 4. FIG. 4 shows an interferencecontroller 402. The components of interference controller 402 will bedescribed herein at a high level using a functional description in orderto convey an understanding of the function of interference controller402. Using this description, one skilled in the art could readilyimplement an interference controller 402 using various hardware,software, and combinations of hardware and software. One suchimplementation could include a programmable computer of the type whichis well known in the art. Returning to FIG. 4, the overall operation ofinterference controller 402 is controlled by a processor 404 whichoperates to control the interference controller 402 by executing storedcomputer program code which defines the desired operation. The storedcomputer program code is stored in storage/memory 410 which may beimplemented using any type of computer readable medium, includingmagnetic, electrical, optical, or other type of media. Processor 404 isalso connected to a database 412 (database 412 is shown separately as afunctional entity, but one skilled in the art will recognize thatdatabase 412 may be implemented using separate storage and logiccomponents, or it may be integrated into storage/memory 410). Database412 defines parameters for frequency masking in order to reduceinterference in the vicinity of the BPL system. These parameters may bedetermined based on the above described compiled spectrum usagecharacteristics.

One particular exemplary data structure for database 412 is shown inFIG. 5. The database 500 shown in FIG. 5 contains various fields whichare used in order to control the masking of frequencies in the BPLsystem. Field 502 contains a time/date range, field 504 containstransmitter/receiver node identifications, and field 506 contains a listof masked frequencies. One exemplary record in database 500 is shown asrecord 510. The time/date range field 502 of record 510 indicates thatthe mask is to be effective on Tuesdays and Fridays from 6-8 pm. As anexample, this type of mask may be used if there is a conflicting user inthe form of a HAM radio operator who operates his/her radio station onlyon Tuesday and Friday evenings. Field 504 of record 510 identifies theparticular BPL transmitter/receiver nodes that are affected by thismask. More particularly, field 504 indicates pairs of adjacenttransmitter/receiver nodes, such that an identified pair of adjacenttransmitter/receiver nodes do not communicate with each other via amasked frequency. In the particular case of record 510, the interferencearea involves the path between two transmitter/receiver nodes (havingidentifications 17436 and 17437). Field 506 identifies the particularfrequency channels to be masked. In the example of FIG. 5, the maskedfrequencies are directly specified, but alternatively the maskedfrequencies may be identified by channel identifiers (e.g., channel A)which have previously been associated with particular frequency ranges.In the example record 510, the frequency range to be masked is thefrequency range of 5-7 MHz. Thus, record 510 indicates that on Tuesdaysand Thursdays between 6 and 8 PM transmitter/receiver nodes 17436 and17437 have a mask on the 5-7 MHz frequency range. One skilled in the artwill recognize that various combinations of data may be present in thedatabase of FIG. 5 in order to contain information which is functionallyequivalent to the information shown in FIG. 5. For example, while therecords of database 500 as described contain the days and times thatcertain frequencies are masked at particular transmitter/receiver nodes,the database could alternatively contain the days and times that certainfrequencies are allowed to be used at particular transmitter/receivernodes. One skilled in the art would recognize that these two uses ofdatabase 500 are functionally equivalent, and that other variousfunctionally equivalent alternatives may also be designed. Further,various additional information may be stored in database 500 in variousimplementations. For example, the name of a HAM (or other) operator aswell as relevant FCC licensing information may be stored.

Returning now to FIG. 4, the interference controller 402 uses theinformation in database 412 in order to determine the necessaryfrequency masking for a BPL system. The interference controller 402utilizes clock 406 in conjunction with database 412 in order todetermine when particular frequency masks need to take affect.Interference controller 402 also contains a network interface 414 whichis used to communicate instructions to the various transmitter/receivernodes in the BPL system. The interface controller 402 may be directlyconnected to the BPL system via a powerline, or alternatively theinterference controller 402 may be connected to the varioustransmitter/receiver nodes via some other network connection (e.g., LAN,WAN, Internet, wireless). Regardless of the particular networkconnection, the interference controller 402, using its clock 406,internal logic and the contents of database 412, determines whenparticular frequency masks need to be implemented at particulartransmitter/receiver nodes, and sends appropriate control instructionsto these particular transmitter/receiver nodes via network interface414. The transmitter/receiver nodes are configured such that uponreceipt of a control instruction from interference controller 402indicating that a particular frequency should be masked, thetransmitter/receiver will stop transmitting and receiving on thatfrequency.

As shown in FIG. 4, interference controller 402 also contains an I/Omodule 408 which represents user interface elements (e.g., keyboard,mouse, display screen, etc.) to allow user interaction with theinterference controller 402. This allows a user to manually modify thecontents of database 412, or to manually send control instructions tothe transmitter/receiver modules.

In another embodiment of the invention, the spectrum characteristics inthe vicinity of the BPL system are monitored in order to determineappropriate frequency masks for the system. In accordance with thisembodiment, the transmitter/receiver nodes monitor the various receivedfrequencies to determine if there is interference (e.g., an incomingsignal above some threshold) present on any of the frequency channels.The monitoring may be done by the BPL system turning off alltransmissions periodically (i.e., a quiet time) and listening for anyreceived signals during this quiet time. If a signal is received duringthe quiet time, then it means that it was received from a conflictinguser, which is an indication of incoming interference on a particularfrequency, and also an indication of possible outgoing interference ifthe BPL system uses the same frequency. The information about the localradio environment as determined by the individual transmitter/receivernodes is then transmitted to the interference controller 402 via itsnetwork interface 414. As described above, the interference controller402 may be directly connected to the BPL system via a powerline, oralternatively the interference controller 402 may be connected to thevarious transmitter/receiver nodes via some other network connection(e.g., LAN, WAN, Internet, wireless).

Upon receipt of the information from the various transmitter/receivernodes, the interference controller 402 determines which frequencychannels to mask for particular transmitter/receiver nodes. In oneembodiment, the interference controller 402 may determine to mask outinterfering frequencies within a particular interference area for aparticular time period. After the time period, the controller 402 mayinstitute another quiet period to listen for interference, and adjustthe frequency masks as necessary to adapt to the new local radioenvironment. The control of the above described monitoring activity maybe controlled and coordinated via the interference controller 402,whereby the interference controller 402 sends appropriate controlinstructions to the transmitter/receiver nodes to control the monitoringand associated masking. For example, the initiation of the quit periodand the monitoring for interference can be performed by thetransmitter/receiver nodes in response to receipt of a controlinstruction from interference controller 402. Alternatively, thetransmitter/receiver nodes could be configured to perform the monitoringon some predetermined schedule. One skilled in the art would recognizethat there are various alternatives possible for this monitoring. Forexample, all frequency channels could be monitored for interferenceduring each quiet period, or alternatively, some subset of the frequencychannels could be monitored.

The monitoring of the local radio environment as described above isparticularly advantageous to detect and compensate for unpredictableinterference situations (e.g., emergency use of various frequencybands).

In accordance with another embodiment of the invention, frequency masksmay be initiated based upon receipt of an indication from a conflictinguser that the user is experiencing interference. In an advantageousembodiment, this is an indication that the conflicting user has receivedan identifier associated with the BPL system. In accordance with thisembodiment, the BPL system periodically transmits a unique identifier onone or more frequencies. The unique identifier may be some code, forexample, that uniquely identifies the BPL system or the service provideroperating the BPL system. The identifier may include other informationas well. The identifier may be pre-programmed into each of thetransmitter/receiver nodes of the system. Alternatively, the identifier,along with an instruction to transmit the identifier, may be sent in acontrol instruction from the interference controller 402.

Upon receipt of interference (including the unique identifier) on aparticular frequency channel, a conflicting user may identify the sourceof interference by associating the received unique identifier with theBPL system and/or the service provider operating the system.Alternatively, the received unique identifier may be provided to a thirdparty (e.g., local government authority) to determine the source ofinterference.

When the service provider operating the BPL system receives anindication that its unique identifier has been received, certainappropriate masking of frequency channels may be initiated. For example,a user may use input/output module 408 of interference controller 402 toimplement appropriate masking to eliminate the interference.Alternatively, a user may use input/output module 408 to add anappropriate record to database 412 as described above so thatappropriate masking will be automatically handled by the interferencecontroller 402 at appropriate times.

The transmission of unique identifiers is advantages to control outboundinterference with respect to conflicting users who are receiving RFsignals, but who are not transmitting signals. The lack of transmissionwould mean that the BPL system would not detect any conflicting use byusing the monitoring techniques described above. As such, thetransmission of an identifier allows the BPL system to mask frequencychannels that are interfering with users who are receiving RF signals,but not transmitting. One advantageous use of this embodiment is in anemergency situation, in which local authorities using a particular radiofrequency are experiencing interference. These authorities couldrecognize the unique identifier and therefore identify the source of theinterference. The authorities could then contact the service provideroperating the BPL system in order to have the service provider mask outthe interfering radio frequencies. Alternatively, the local authoritiescould have direct access to the interference controller 402 (e.g., vianetwork interface 414) and could immediately mask out the interferingradio frequencies themselves. In severe emergency situations, the localauthorities could even shut down all RF transmissions on the BPL systemvia access to the interference controller 402.

The foregoing Detailed Description is to be understood as being in everyrespect illustrative and exemplary, but not restrictive, and the scopeof the invention disclosed herein is not to be determined from theDetailed Description, but rather from the claims as interpretedaccording to the full breadth permitted by the patent laws. It is to beunderstood that the embodiments shown and described herein are onlyillustrative of the principles of the present invention and that variousmodifications may be implemented by those skilled in the art withoutdeparting from the scope and spirit of the invention. Those skilled inthe art could implement various other feature combinations withoutdeparting from the scope and spirit of the invention. For example, inaddition to the masking of certain frequency channels as describedabove, it is also possible to initiate data transmission on alternatefrequency channels upon a determination that certain frequency channelsneed to be masked. Further, one skilled in the art would recognize thatvarious combinations of embodiments are also possible in accordance withthe principles of the present invention.

The invention claimed is:
 1. A method of operation of a broadbandpowerline communication system that is transmitting data over apredetermined range of modulated carrier frequencies not usedexclusively by the broadband powerline communication system, the methodcomprising: turning off transmissions over the predetermined range ofmodulated carrier frequencies in response to a control instruction;determining spectrum characteristics of a radio environment over thepredetermined range of modulated carrier frequencies in a vicinity ofthe broadband powerline communication system after turning off thetransmissions; compiling a database of the spectrum characteristicscomprising characteristics of usage of the predetermined range ofmodulated carrier frequencies by conflicting users in the vicinity ofthe broadband powerline communication system, the characteristics ofusage of the predetermined range of modulated carrier frequenciescomprising: a geographical area in which each of the conflicting usersinterferes with the broadband powerline communication system; and acombination of time intervals and carrier frequencies used by each ofthe conflicting users in the vicinity of the broadband powerlinecommunication system; generating a schedule of use of the thepredetermined range of modulated carrier frequencies by each of theconflicting users based on the characteristics of the usage of thepredetermined range of modulated carrier frequencies by the conflictingusers in the vicinity of the broadband powerline communication system;and masking certain ones of the predetermined range of carrierfrequencies between particular pairs of adjacent nodes in the broadbandpowerline communication system based on the schedule.
 2. The method ofclaim 1 wherein determining the spectrum characteristics furthercomprises: monitoring the radio environment to detect conflicting users.3. The method of claim 1 wherein determining the spectrumcharacteristics further comprises: receiving an indication from a userthat the user has received an identifier on a particular frequency at aparticular location.
 4. Apparatus for controlling interference in abroadband powerline communication system that is transmitting data overa predetermined range of modulated carrier frequencies not usedexclusively by the broadband powerline communication system, theapparatus comprising: a processor; and a memory storing computer programinstructions, the computer program instructions when executed on theprocessor cause the processor to perform operations comprising: turningoff transmissions over the predetermined range of modulated carrierfrequencies in response to a control instruction; determining spectrumcharacteristics of a radio environment over the predetermined range ofmodulated carrier frequencies in a vicinity of the broadband powerlinecommunication system after turning off the transmissions; compiling adatabase of the spectrum characteristics comprising characteristics ofusage of the predetermined range of modulated carrier frequencies byconflicting users in the vicinity of the broadband powerlinecommunication system, the characteristics of usage of the predeterminedrange of modulated carrier frequencies comprising: a geographical areain which each of the conflicting users interferes with the broadbandpowerline communication system; and a combination of time intervals andcarrier frequencies used by each of the conflicting users in thevicinity of the broadband powerline communication system; generating aschedule of use of the the predetermined range of modulated carrierfrequencies by each of the conflicting users based on thecharacteristics of the usage of the predetermined range of modulatedcarrier frequencies by the conflicting users in the vicinity of thebroadband powerline communication system; and masking certain ones ofthe predetermined range of carrier frequencies between particular pairsof adjacent nodes in the broadband powerline communication system basedon the schedule.
 5. The apparatus of claim 4 further comprising: aplurality of transmitter/receiver nodes for monitoring signals receivedvia the broadband powerline communication system.
 6. The apparatus ofclaim 4 further comprising a controller node sending controlinstructions to transmitter/receiver nodes.
 7. A method for controllinginterference in a broadband powerline communication system that istransmitting data over a predetermined range of modulated carrierfrequencies not used exclusively by the broadband powerlinecommunication system, the method comprising: transmitting transmissioncontrol instructions to one of a plurality of transmitter/receiver nodesin the broadband powerline communication system to turn offtransmissions over the predetermined range of modulated carrierfrequencies; accessing a database storing characteristics of usage ofthe predetermined range of modulated carrier frequencies by conflictingusers in a vicinity of the broadband powerline communication system, thecharacteristics of usage of the predetermined range of modulated carrierfrequencies comprising: a geographical area in which each of theconflicting users interferes with the broadband powerline communicationsystem; and a combination of time intervals and carrier frequencies usedby each of the conflicting users in the vicinity of the broadbandpowerline communication system; determining frequency masking parametersbased on the characteristics of usage of the predetermined range ofmodulated carrier frequencies by conflicting users in a vicinity of thebroadband powerline communication system after turning off thetransmissions; comparing the frequency masking parameters to currentdate/time information; and transmitting frequency mask controlinstructions to particular pairs of adjacent transmitter/receiver nodesin the broadband powerline communication system to mask certain ones ofthe predetermined range of carrier frequencies between the particularpairs of adjacent transmitter/receive nodes in the broadband powerlinecommunication system based on the comparison of the frequency maskingparameters to current date/time information, such that other pairs ofadjacent nodes in the broadband powerline communication system continueto transmit data over the certain ones of the predetermined range ofcarrier frequencies.
 8. The method of claim 7 wherein the frequencymasking parameters comprise: an identification of particular ones of theplurality of transmitter/receiver nodes and associated frequencychannels.
 9. The method of claim 8 wherein the frequency maskingparameters further comprise: time/date information indicating particulartimes to effect frequency masking.
 10. Apparatus for controllinginterference in a broadband powerline communication system that istransmitting data over a predetermined range of modulated carrierfrequencies not used exclusively by the broadband powerlinecommunication system, the apparatus comprising: a processor; and amemory to store computer program instructions, the computer programinstructions when executed by the processor cause the processor toperform operations comprising: transmitting transmission controlinstructions to one of the plurality of transmitter/receiver nodes inthe broadband powerline communication system to turn off transmissionsover of the predetermined range of modulated carrier frequencies;storing characteristics of usage of the predetermined range of modulatedcarrier frequencies by conflicting users in a vicinity of the broadbandpowerline communication system, the characteristics of usage of thepredetermined range of modulated carrier frequencies comprising: ageographical area in which each of the conflicting users interferes withthe broadband powerline communication system; and a combination of timeintervals and carrier frequencies used by each of the conflicting usersin the vicinity of the broadband powerline communication system;determining frequency masking parameters based on the characteristics ofusage of the predetermined range of modulated carrier frequencies byconflicting users in a vicinity of the broadband powerline communicationsystem after turning off the transmissions; and transmitting controlinstructions to particular pairs of adjacent transmitter/receiver nodesto mask certain ones of the predetermined range of carrier frequenciesbetween the particular pairs of adjacent transmitter/receive nodes inthe broadband powerline communication system based on the frequencymasking parameters, such that other pairs of adjacent nodes in thebroadband powerline communication system continue to transmit data overthe certain ones of the predetermined range of carrier frequencies. 11.The apparatus of claim 10 wherein the frequency masking parameterscomprise: an identification of particular ones of the plurality oftransmitter/receiver nodes and associated frequency channels.
 12. Theapparatus of claim 11 wherein the frequency masking parameters furthercomprise: time/date information indicating particular times to effectfrequency masking.
 13. A method for controlling interference in abroadband powerline communication system that is transmitting data overa predetermined range of modulated carrier frequencies not usedexclusively by the broadband powerline communication system, the methodcomprising: transmitting transmission control instructions to particularpairs of adjacent transmitter/receiver nodes in the broadband powerlinecommunication system to turn off transmissions over the predeterminedrange of modulated carrier frequencies; monitoring the radio environmentover the predetermined range of modulated carrier frequencies in avicinity of the broadband powerline communication system to detectconflicting users after turning off the transmissions; generating aschedule of use of the predetermined range of modulated carrierfrequencies by each of the conflicting users based on characteristics ofusage of the predetermined range of modulated carrier frequencies by theconflicting users in the vicinity of the broadband powerlinecommunication system; and masking certain ones of the predeterminedrange of carrier frequencies between the particular pairs of adjacenttransmitter/receive nodes in the broadband powerline communicationsystem based on the schedule.
 14. The method of claim 13 whereinmonitoring the radio environment is performed by the plurality oftransmitter/receiver nodes of the broadband powerline communicationsystem.
 15. The method of claim 14 further comprising: the plurality oftransmitter/receiver nodes transmitting conflicting user information tothe controller node.
 16. The method of claim 14 wherein monitoring theradio environment is performed periodically by the plurality oftransmitter/receiver nodes.
 17. The method of claim 16 wherein theplurality of transmitter/receiver nodes stop transmitting whilemonitoring the radio environment.
 18. The method of claim 14 whereinmonitoring the radio environment is performed by the plurality oftransmitter/receiver nodes in response to receipt of a controlinstruction from the controller node.